For various reasons crops sometimes are lying so close to the ground that it is difficult to cut them with a conventional harvest header. Some crops are inherently short, while others may be taller, but are prone to fall down when they reach maturity.
Typically the knife on cutting headers comprises a knife bar extending along the front lower edge of the header, with a plurality of triangular knife sections attached to the bar such that the apex of the triangle extends forward from the bar. The exposed side edges of the knife sections are sharpened. Guards are attached to the front lower edge of the header and serve to protect the knife sections from breakage when contacting stones and like obstructions. The guards comprise pointed guard fingers extending forward, and the knife moves back and forth along the edge of the header in a slot cut laterally through the guard fingers. In addition to protecting the knife, the guard fingers also enable the knife sections to cut the crop. As the knife section moves back and forth it pushes crop against the sides of those portions of the guard finger that are above and below the slot, shearing the crop stalks.
A conventional knife is a few inches above the ground when the header is in its lowest position, such that very short or downed crop material will pass under the knife and be lost. Many different kinds of “crop lifters”, as they have come to be known have been developed over the last century and more. Typically these crop lifters are attached to the header and/or the forward extending point of the guard finger, and provide an arm of various designs that rides along the ground ahead of the knife. A lifting finger extends at a shallow angle from the front of the arm back and over the knife. As the header moves down the field, the arm rides along the ground and under the downed crop stalks, which then are lifted and pass over the lifting finger to the knife, where they are cut and continue moving onto the header from where they can be passed to the harvester, swather table, or the like.
U.S. Pat. Nos. 700,029 and 791,022 to Gatermann disclose such a crop lifter that is pivotally attached to the header so as to be able to move up and down to follow the ground. U.S. Pat. No. 4,120,138 to Schumacher illustrates a crop lifter that is fixed to the header instead of pivoting, but is made of spring steel so that same may move up and down to follow the ground.
Much loss often occurs in straight cut harvesting of crops such as dry beans, peas, and lentils due to pods shattering or pods, or parts of pods that are below the cutter bar. The lifting fingers of the prior art are narrow fingers that are designed to lift stalks above the knife so that they may be cut, and so that the seed pods attached to the stalks may be carried onto the header and retained. The narrow fingers however allow pods to hang down on each side of the rod as the stalk moves rearward along the finger, such that some pods are below the knife when the stalk is cut, and therefore drop to the ground and are lost.
As well, seed pods often shatter when contacted by the harvesting equipment before they are on the header, and the shattered pods spill their seeds to fall on the ground. The crop lifters are moving relatively slowly at the speed of the harvester, perhaps five miles per hour, but the knife is moving rapidly back and forth in the guards. Thus most of the shattering loss occurs in the area generally just above the knife when the stalk is contacted by the rapidly moving knife. Seeds fall from the shattered pods down through the knife to the ground. While this problem of shattering seed pods and heads is more severe in some crops than others, there is generally at least some shattering loss in any crop.
It is therefore known to attach wide seed pans to the cutting header, as disclosed in U.S. Pat. Nos. 4,255,920 to Janzen, 5,105,610 to Britten, and 6,564,536 to Hoffer. These pans extend forward from the knife to a pointed front end, with parallel edges of the pans separated by a slot along which crop plants move to the knife. The seed pans cover part of the knife, such that plants are cut only by that portion of the knife that is exposed at the end of the slots. These pans are also referred to as divider pans or guide pans and they divide and guide crop plants to the exposed portions of the knife. Seeds falling from the plants also fall onto the wide pans and are swept onto the cutting header.